Move SetupMetrics() to PreMainMessageLoopRun

ios/chrome/browser/ios_chrome_main_parts.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ios/chrome/browser/ios_chrome_main_parts.h"
 
 #include "base/base_switches.h"
 #include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ skipping 114 matching lines @@
   // the calls below end up implicitly creating threads and as such new calls
   // typically either belong before them or in a later startup phase.
 
   // Now that the command line has been mutated based on about:flags, we can
   // initialize field trials and setup metrics. The field trials are needed by
   // IOThread's initialization in ApplicationContext's PreCreateThreads.
   SetupFieldTrials();
 
   // Task Scheduler initialization needs to be here for the following reasons:
   //   * After |SetupFieldTrials()|: Initialization uses variations.
-  //   * Before |SetupMetrics()|: |SetupMetrics()| uses the blocking pool. The
-  //         Task Scheduler must do any necessary redirection before then.
   //   * Near the end of |PreCreateThreads()|: The TaskScheduler needs to be
   //         created before any other threads are (by contract) but it creates
   //         threads itself so instantiating it earlier is also incorrect.
   // To maintain scoping symmetry, if this line is moved, the corresponding
   // shutdown call may also need to be moved.
   task_scheduler_util::InitializeDefaultBrowserTaskScheduler();
 
-  SetupMetrics();
 
   // Initialize FieldTrialSynchronizer system.
   field_trial_synchronizer_.reset(new ios::FieldTrialSynchronizer);
 
   application_context_->PreCreateThreads();
 }
 
 void IOSChromeMainParts::PreMainMessageLoopRun() {
+  // This must occur at PreMainMessageLoopRun because |SetupMetrics()| uses the
+  // blocking pool, which is disabled until the CreateThreads phase of startup.
+  SetupMetrics();
+
   // Now that the file thread has been started, start recording.
   StartMetricsRecording();
 
   application_context_->PreMainMessageLoopRun();
 
   // ContentSettingsPattern need to be initialized before creating the
   // ChromeBrowserState.
   ContentSettingsPattern::SetNonWildcardDomainNonPortScheme(
       kDummyExtensionScheme);
 
@@ skipping 138 matching lines @@
 
 void IOSChromeMainParts::StartMetricsRecording() {
   bool wifiOnly = local_state_->GetBoolean(prefs::kMetricsReportingWifiOnly);
   bool isConnectionCellular = net::NetworkChangeNotifier::IsConnectionCellular(
       net::NetworkChangeNotifier::GetConnectionType());
   bool mayUpload = !wifiOnly || !isConnectionCellular;
 
   application_context_->GetMetricsServicesManager()->UpdateUploadPermissions(
       mayUpload);
 }